Cytogenetic analysis of human embryos and embryonic stem cells derived from monopronuclear zygotes

Abstract

Purpose By comparing the chromosomal constitution among the arrested cleavage-stage embryos, blastocysts and human embryonic stem cells (hESCs) which are all derived from monopronuclear (1PN) zygotes, it is aimed to determine whether chromosomally normal embryos can be reliably selected by blastocyst culture. Methods After 1PN zygotes are sequentially cultured for 5 days, the blastocysts and arrested cleavage-stage embryos were analyzed by fluorescence in situ hybridization (FISH) with probes for chromosomes 18, X and Y; G-banding analysis was adopted to analyze the karyotype of 1PN hESCs.Results The diploid rate of blastocysts was 74.6%, which was significantly (P<0.001) higher than that of arrested cleavage-stage embryos (31.6%), and the diploid rate of hESCs was 97.0%, which was significantly (P < 0.01) higher than that of blastocysts; the haploid embryos were excluded by blastocyst culture; nevertheless, there still existed such chromosomal abnormalities as mosaic and monosomic in blastocysts and trisomy in hESCs. Conclusions Blastocyst culture is an effective method to select against chromosomal abnormalities, especially the haploids in 1PN embryos; however, development to the blastocyst stage is not a reliable marker for mosaicism or aneuploidy.

Pronuclear removal of tripronuclear zygotes can establish heteroparental normal karyotypic human embryonic stem cells

“…During blastocyst culture, the diploid rate of blastocysts from the microsurgically corrected 3PN zygotes increased to 55.0 %, significantly higher than the diploid rate of the arrested cleavage-stage embryos (18.4 %), and the mosaic rate of the blastocysts (30.0 %) was significantly lower than that of the arrested cleavage-stage embryos (59.2 %), although chromosomal abnormalities, such as mosaic, polyploidy, and aneuploidy, remained. These results indicate that blastocyst culture is an effective method for selecting against embryos with abnormal chromosomal constitution, consistent with previous studies that have observed that the developmental potential of chromosomal abnormal embryos to the morula and blastocyst stage is significantly lower than that of normal karyotypic embryos [33][34][35][36][37]. The possible mechanism of selection is apoptosis, a common mechanism by which human embryos eliminate abnormal cells [38].…”

Clinical outcomes of transfer of frozen and thawed single blastocysts derived from nonpronuclear and monopronuclear zygotes

“…However, the implantation rates were nearly the same with blastocyst transfer. Liao et al, reported a significantly higher diploidy rate for 1PN‐derived blastocysts (74.6%) than for 1PN with halted cleavage (31.6%). In previous reports, the fractions of embryos reaching the blastocyst stage were low, 16.7%‐35.0%, for 0PN and 3.6%‐21.4% for 1PN, suggesting that embryos with aberrant chromosomes may be eliminated during the blastocyst culture process.…”

“…In previous reports, the fractions of embryos reaching the blastocyst stage were low, 16.7%‐35.0%, for 0PN and 3.6%‐21.4% for 1PN, suggesting that embryos with aberrant chromosomes may be eliminated during the blastocyst culture process. However, Liao et al, reported that elimination of haploids, but not mosaic embryos and polyploids, is possible by blastocyst transfer, showing that the safety of 1PN or 0PN embryos cannot be ensured simply based on blastocyst stage.…”

Birth of nine normal healthy babies following transfer of blastocysts derived from human single-pronucleate zygotes

“…Several attempts to analyze human 1PN zygotes and embryos in cIVF and ICSI cycles have been reported, such as the mechanism of 1PN formation on fertilization [4,6,[16][17][18]; chromosome constitution in zygote, embryo, and blastocyst stages [6,9,10,12,[19][20][21]; and genetic composition of the pronucleus in human [11] and mouse [22]. According to these data, when the chromosomal status of 1PN embryos was analyzed using fluorescence in situ hybridization (FISH), the rate of diploid chromosome constitution in cIVF was significantly higher than that in ICSI [6,9,10].…”

“…Further, they reported that the rate of diploid chromosomes in 1PN zygotes were 86.7 % in cIVF and 30.3 % in ICSI [11]. Moreover, Liao et al reported that the diploid rate of blastocysts derived from 1PN embryos was significantly higher than in arrested cleavage-stage embryos [12]. Although there have been several reports analyzing the chromosome constitution of embryos derived from 1PN by FISH or immunostaining, there is little embryological and clinical data for 1PN embryos.…”